Experimental research on heat transfer enhancement and associated bubble characteristics under high-frequency reciprocating flow

An experimental research was conducted to study the effects of high-frequency reciprocating flow on subcooled boiling heat transfer performance on a chip using FC-72 in a horizontal rectangular narrow channel with a hydraulic diameter of 7.5 mm. In the experiments, the flow velocity varied from 0.25 to 0.95 m/s for the inlet liquid subcooling of 35 degrees C, and the frequency was from 0 to 10 Hz. The result indicates that the flow reciprocation can improve heat transfer performance in the low and high heat flux regions, but has limited effect under medium heat flux. The CHF of reciprocating flow has a tendency to increase with the increase of Reynolds number and Strouhal number. The maximum improvement of CHF is 42.3% with the flow velocity of 0.5 m/s and the frequency of 10 Hz. Photographic studies showed that bubbles under reciprocating flow are much smaller because of the limited growth time and the alternative variation of the flow field. (C) 2019 Elsevier Ltd. All rights reserved.